The Rest of the Story
On Apr 11, 9:25*am, Cecil Moore wrote:
Keith Dysart wrote:
The computation using energy instead of power has
also been done (and published here) and found also
to demonstrate that the reflected is not dissipated
in the source resistor.
Well, that certainly violates the conservation of
energy principle. We know the reflected energy is
not dissipated in the load resistor, by definition.
The only other device in the entire system capable
of dissipation is the source resistor. Since the reflected
energy is not dissipated in the load resistor and you say
it is not dissipated in the source resistor, it would
necessarily have to magically escape the system or build
up to infinity (but it doesn't).
You seem to have forgotten that a voltage source can
absorb energy. This happens when the current flows
into it rather than out.
Recall the equation
Ps(t) = Prs(t) + Pg(t)
When the voltage source voltage is greatr than the
voltage at the terminals of the line (Vg(t)), energy
flows from the source into the resistor and the line.
When the voltage at the line terminals is greater
than the voltage source voltage, energy flows from
the line into the resistor and the voltage source.
At all times
Ps(t) = Prs(t) + Pg(t)
holds true.
Conservation of energy at work. No lost energy.
gartuitous comment snipped
How many joules are there in 100 watts of
instantaneous power?
Obviously. It depends on how long you let the
100 W of instantaneous power flow. Integrate and
the answer shall be yours.
I'm not the one making the assertions. How many joules
of energy exist in *YOUR* instantaneous power calculations?
We have been down that path; the spreadsheet has been
published. The flows of energy described by
Ps(t) = Prs(t) + Pg(t)
always balance.
The integration of these energy flows over any interval
also balance.
Energy is conserved. The world is as it should be.
...Keith
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